yes, me too!! Ive thought about that. They have to adress where do they live now.

Magneto said at the end of First Class that they would build their own mutant society, so it might be an opportunity to show the creation of the nation of Genosha.

I loved the comic book bases that Magneto used, such as the one underneath a volcano and the Atlantis island raised from the sea in the Bermuda Triangle - but those are probably a bit 'way out' like something from an old James Bond movie.